1. Field of the Invention
The present invention relates to a sputtering device used in the fabrication of various types of semiconductor devices. More particularly, it relates to an ionizing sputtering device having a function that ionizes the sputter particles.
2. Description of Related Art
With semiconductor devices, such as various types of memory and logic, a sputtering process is used in the formation of various wiring films, and in the production of barrier films that prevent the interdiffusion of different layers. A sputtering process makes use of a sputtering device, and there has recently been a great need for such sputtering devices to allow the inner surfaces of holes formed in a substrate to be coated with a good degree of coverage.
Recently, there has been a need in the case of barrier films for an increase in the bottom coverage, which is the ratio of the film deposition on the bottom of a hole to that on the peripheral surfaces of the hole. With today's higher degrees of integration, holes such as contact holes have been steadily increasing in aspect ratio, which is the ratio of the hole depth to the size of the hole opening. A film cannot be deposited with good bottom coverage by a conventional sputtering process. A decrease in the bottom coverage can lead to a thinner barrier film at the bottom of the hole and to critical flaws in the device characteristics, such as junction leakage.
Collimation sputtering, and low-pressure, long-distance sputtering, have been developed up to now as sputtering processes that increase the bottom coverage. These processes will not be described in detail here, but they all attempt to direct many neutral sputter particles perpendicularly at the substrate.
A problem with collimation sputtering, however, is that sputter particles accumulate on the collimator portion, and the resulting loss of material decreases the film deposition rate. A problem with low-pressure, long-distance sputtering is that since the pressure is lowered and the distance between the target and the substrate is lengthened, there is a fundamental decrease in the film deposition rate. Because of these problems, the first generation is about as far as these processes are expected to go, or up to 64 megabits with collimation sputtering and 256 megabits with low-pressure, long-distance sputtering.
There is a need for a practical process that can be utilized in the production of devices over 256 megabits. In response to this need, there has been speculation that ionizing sputtering might be a useful process. Ionizing sputtering is a process in which the sputter particles released from the target are ionized, and the sputter particles are made to arrive inside the hole more efficiently through the action of these ions. Ionizing sputtering yields a higher bottom coverage than collimation sputtering or low-pressure, long-distance sputtering.
Typically, ionizing sputtering involves forming a plasma along the flight path of the sputter particles between the substrate and the target, and ionizing the sputter particles as they pass through the plasma. An inductive coupling type of plasma is usually formed as this plasma. In specific terms, a high frequency coil is provided such that it surrounds the space where the ionization is performed along the flight path, hereinafter referred to as the ionization space. Constant high frequency waves are supplied to this high frequency coil to form a plasma on the inside of the high frequency coil. High frequency current flows into the plasma, and the plasma and the high frequency coil are inductively coupled. It is because of this action that this plasma is called an inductive coupling type of plasma.